An automatic analyzer for analyzing components in blood, urine, and the like is configured to dispense a liquid specimen and a reagent into a reaction cuvette to cause a chemical reaction, irradiate a reaction liquid with light by means of a halogen lamp or the like, and measure absorbance to analyze components in the liquid specimen.
A nozzle is used to dispense the sample and the reagent into the reaction cuvette. As water filling this nozzle, purified water supplied from a water purifying unit to a water feed tank of the analyzer is used and is called system water. A suction sequence is produced to prevent the sample and the reagent from contacting the system water in the nozzle and provide segmenting air therebetween.
When the sample and the system water move inside the nozzle during dispensation, movement between the sample and the system water may occur via an inner wall of the nozzle, and dilution of the sample may occur. To keep the dilution amount within an allowance, a dummy suction technique for sucking the sample excessively is disclosed (PTL 1).
Also, to prevent carry-over between samples, an internal cleaning operation for cleaning the inside of the nozzle is performed at the time of dispensing one sample and then another sample. The internal cleaning operation is performed with use of a high-pressure pump since the system water needs to be pushed out under high pressure for sufficient internal cleaning.